[PATCH 1/2] Modify cpupower to schedule itself on cores it is reading MSRs from

[Natarajan, Janakarajan]

Modify cpupower to schedule itself on each of the cpus in the system and
then get the APERF/MPERF register values.

This is advantageous because an IPI is not generated when a read_msr() is
executed on the local logical CPU thereby reducing the chance of having
APERF and MPERF being out of sync.

Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@xxxxxxx>
---
 .../utils/idle_monitor/mperf_monitor.c        | 38 ++++++++++++++-----
 1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
index 44806a6dae11..8b072e39c897 100644
--- a/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
+++ b/tools/power/cpupower/utils/idle_monitor/mperf_monitor.c
@@ -10,6 +10,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
+#include <sched.h>
 
 #include <cpufreq.h>
 
@@ -86,15 +87,33 @@ static int mperf_get_tsc(unsigned long long *tsc)
 	return ret;
 }
 
+static int get_aperf_mperf(int cpu, unsigned long long *aval,
+			   unsigned long long *mval)
+{
+	cpu_set_t set;
+	int ret;
+
+	CPU_ZERO(&set);
+	CPU_SET(cpu, &set);
+	if (sched_setaffinity(getpid(), sizeof(set), &set) == -1) {
+		dprint("Could not migrate to cpu: %d\n", cpu);
+		return 1;
+	}
+
+	ret = read_msr(cpu, MSR_APERF, aval);
+	ret |= read_msr(cpu, MSR_MPERF, mval);
+
+	return ret;
+}
+
 static int mperf_init_stats(unsigned int cpu)
 {
-	unsigned long long val;
+	unsigned long long aval, mval;
 	int ret;
 
-	ret = read_msr(cpu, MSR_APERF, &val);
-	aperf_previous_count[cpu] = val;
-	ret |= read_msr(cpu, MSR_MPERF, &val);
-	mperf_previous_count[cpu] = val;
+	ret = get_aperf_mperf(cpu, &aval, &mval);
+	aperf_previous_count[cpu] = aval;
+	mperf_previous_count[cpu] = mval;
 	is_valid[cpu] = !ret;
 
 	return 0;
@@ -102,13 +121,12 @@ static int mperf_init_stats(unsigned int cpu)
 
 static int mperf_measure_stats(unsigned int cpu)
 {
-	unsigned long long val;
+	unsigned long long aval, mval;
 	int ret;
 
-	ret = read_msr(cpu, MSR_APERF, &val);
-	aperf_current_count[cpu] = val;
-	ret |= read_msr(cpu, MSR_MPERF, &val);
-	mperf_current_count[cpu] = val;
+	ret = get_aperf_mperf(cpu, &aval, &mval);
+	aperf_current_count[cpu] = aval;
+	mperf_current_count[cpu] = mval;
 	is_valid[cpu] = !ret;
 
 	return 0;
-- 
2.17.1